Materials.
O-Ring Materials: An Introduction
Material compounds
NBR (Nitrile Butadiene Rubber)
FKM (Fluorocarbon / Viton®)
EPDM (Ethylene Propylene Diene Monomer)
VMQ (Silicone Rubber)
HNBR (Hydrogenated Nitrile Butadiene Rubber)
FFKM (Perfluoroelastomer)
PTFE (Polytetrafluoroethylene)
Polyurethane – Cast (AU)
Polyurethane – Thermoplastic (TPU / EU)
ACM (Polyacrylate Rubber)
CR (Chloroprene / Neoprene®)
VMQ (Fluorosilicone Rubber)
At orings.co.uk, we supply all the base materials commonly used for O-rings – including NBR, FKM (Viton®), EPDM, Silicone, HNBR, PTFE, and more. Each material comes with its own advantages depending on temperature range, chemical compatibility, and mechanical requirements.
Beyond the basics, there are thousands of manufacturer-specific compounds that fine-tune performance even further. These proprietary blends vary in:
Hardness (Shore A)
Compression set resistance
Tensile strength
Wear and abrasion resistance
Low temperature flexibility
Chemical and fluid resistance
We make it simple. You get the right seal, first time.
We supply O-rings in a full range of standard and specialist material compounds, matched to the performance requirements of each application. Whether the priority is chemical resistance, temperature tolerance, flexibility, or long-term durability, we work with a proven network of manufacturers to deliver the right compound for your specification.
Our most commonly sourced material compounds include Nitrile (NBR), Viton® (FKM), EPDM, Silicone, and PTFE, with additional options such as FFKM and HNBR available for high-performance or aggressive environments. Each compound is available in multiple hardness grades and can be supplied with relevant certifications on request. Selection is based on compatibility with your media, temperature range, and required lifecycle.
We do not promote “general purpose” stock. Instead, we procure to order, ensuring the correct material compound is supplied every time — from reputable sources with traceable batch data where required. If you are unsure of the exact compound needed, we are happy to assist with guidance or review your existing specification.
NBR (Nitrile Butadiene Rubber) is the most commonly used elastomer for O-rings, due to its excellent resistance to petroleum-based oils, fuels, greases, and hydraulic fluids. It performs reliably in temperatures ranging from -30°C to +100°C, with some special grades extending lower. NBR offers good abrasion resistance, mechanical strength, and compression set properties, making it ideal for dynamic and static applications. Available in a wide range of hardnesses, NBR can be tailored to meet application-specific requirements such as fuel resistance, food contact approval, or improved low-temperature flexibility. However, it has limited resistance to ozone, UV, and weathering, and is not suitable for polar solvents or brake fluids. NBR is widely used in automotive, industrial, and hydraulic applications, and remains the sealing material of choice for many engineers. Thousands of proprietary NBR compounds exist, with variations in filler systems, cross-linking agents, and additives to enhance specific performance characteristics. These include improved ageing, chemical resistance, and fluid compatibility. Standard black NBR is often used for general-purpose sealing, while coloured or certified grades meet more demanding specifications. We supply both standard and specialist NBR compounds depending on the application's demands.
FKM is a high-performance fluoroelastomer known for its excellent chemical, heat, and oil resistance. It operates reliably in temperatures from -20°C to +200°C, with some grades handling even higher. FKM is widely used in automotive, aerospace, and industrial applications where aggressive fluids or high temperatures are involved. It resists most hydrocarbons, lubricants, fuels, and many solvents, making it ideal for sealing in demanding environments. FKM has low gas permeability and excellent ageing characteristics, even in ozone and weather-exposed conditions. However, it is not suitable for steam, glycol-based brake fluids, or certain polar solvents. FKM is available in multiple grades, including low-temperature, fuel-resistant, peroxide-cured, and FDA-approved variants. Shore A hardness typically ranges from 60 to 90. Compression set and extrusion resistance are good, particularly in static applications. Specialist FKM compounds are used in aggressive chemical processes or ultra-high vacuum systems. We supply standard black FKM as well as premium grades for critical sealing tasks.
EPDM is a synthetic elastomer prized for its excellent resistance to weathering, ozone, and a wide range of polar fluids. It performs across a broad temperature range from -50°C to +150°C, making it ideal for steam, water, glycol, brake fluid (non-mineral), and outdoor applications. EPDM is not compatible with petroleum oils, fuels, or most hydrocarbons. It exhibits excellent compression set resistance and long service life in both dynamic and static conditions. EPDM is widely used in automotive cooling systems, drinking water installations, HVAC systems, and food-grade applications. Available in peroxide- or sulfur-cured versions, with peroxide grades offering enhanced thermal and ageing performance. Shore A hardness usually ranges from 50 to 90. EPDM can be compounded to meet WRAS, FDA, and other regulatory approvals. White and coloured compounds are available for aesthetic or compliance needs. We supply a range of EPDM grades including steam-resistant and drinking-water certified types.
Silicone rubber (VMQ) is known for its exceptional flexibility and stability across extreme temperature ranges, typically -60°C to +200°C. It is particularly suited to food, medical, and static sealing applications where cleanliness and low toxicity are critical. Silicone offers excellent resistance to oxygen, ozone, and UV radiation, but has poor resistance to fuels, oils, and most solvents. Its low compression set and inert properties make it ideal for use in life sciences, electronics, and lighting applications. VMQ compounds are generally soft (Shore A 40–80) and less abrasion-resistant than other elastomers, limiting their use in dynamic applications. Food- and medical-grade silicones are widely available, including platinum-cured types for sensitive environments. Transparent and colour-matched options can be produced for aesthetic or compliance purposes. Silicone is non-reactive and performs well under sterilisation, thermal cycling, and cleanroom conditions. We supply both peroxide- and platinum-cured VMQ for technical, pharmaceutical, and cosmetic use.
ANBR is a highly saturated nitrile rubber offering improved heat, ozone, and chemical resistance compared to standard NBR. It performs well in temperatures from -40°C to +150°C and combines the oil resistance of NBR with enhanced physical and mechanical properties. HNBR is often used in high-performance automotive, HVAC, and industrial systems where long life and elevated temperatures are a concern. It provides superior wear resistance, tensile strength, and tear resistance, making it suitable for dynamic sealing. HNBR compounds exhibit excellent compatibility with engine oils, ATFs, coolants, and refrigerants, including R134a and R1234yf. It is not suitable for aromatic fuels or polar solvents. Shore A hardness typically ranges from 50 to 90. HNBR is available in peroxide-cured versions for improved thermal and chemical resistance. We offer general-purpose and specialist HNBR compounds for applications requiring higher performance than NBR.
FFKM offers the highest chemical and thermal resistance of any elastomer, suitable for use in aggressive chemical environments and ultra-high temperatures. It operates continuously from +5°C to +315°C, with some grades handling intermittent exposure beyond 327°C. FFKM is chemically compatible with almost all fluids, including strong acids, ketones, esters, amines, solvents, and fuels. It has extremely low gas permeability and outstanding thermal ageing performance. FFKM is widely used in semiconductor, pharmaceutical, and aerospace industries where sealing failure is unacceptable. Its compression set resistance is excellent, but cost is significantly higher than other elastomers. FFKM is ideal for vacuum applications, aggressive chemical processing, and cleanroom environments. FDA- and USP-compliant grades are available for high-purity use. Shore A hardness generally ranges from 60 to 90. We supply high-grade FFKM compounds from specialist manufacturers for mission-critical applications.
PTFE is a chemically inert, non-elastomeric sealing material with exceptional resistance to nearly all chemicals and solvents. It has an extremely wide temperature range, typically from -200°C to +260°C, and is non-reactive even in highly aggressive environments. PTFE has the lowest coefficient of friction of any solid material, making it ideal for dynamic sealing where lubrication is limited. It is non-stick, non-toxic, and approved for food, medical, and pharmaceutical applications. However, PTFE is not elastic and does not return to shape like a traditional rubber O-ring. It is prone to cold flow (creep) under pressure, and typically requires energizers or mechanical support in dynamic use. PTFE O-rings are used in static, high-purity, or chemically aggressive systems. Virgin PTFE, filled PTFE (e.g., glass, carbon, bronze), and modified grades are available depending on mechanical and thermal requirements. We supply precision-machined PTFE seals for critical environments where elastomers fall short.
Cast polyurethane (AU) is a tough, wear-resistant elastomer used in heavy-duty sealing applications. It has high tensile strength, excellent abrasion resistance, and very low gas permeability, making it suitable for hydraulic and high-pressure environments. Typical temperature range is -30°C to +100°C, with some formulations extending higher. Cast PU resists oil and fuel moderately well, but is sensitive to water and hydrolysis unless specially stabilised. It is widely used in hydraulic seals, scrapers, pneumatic tools, and shock-absorbing components. Hardness typically ranges from Shore A 70 to Shore D 60. Cast polyurethane can be machined or moulded and offers dimensional stability under load. It is not suitable for high temperatures or chemically aggressive environments. We provide a range of precision-machined cast PU components for use in cylinders, pumps, and hydraulic systems.
Thermoplastic polyurethane (TPU, also referred to as EU) is a versatile material used for O-rings, wipers, and seals requiring a combination of flexibility and toughness. It has excellent abrasion resistance, tear strength, and low-temperature flexibility (down to -50°C), while also offering moderate oil and fuel resistance. TPU operates within a typical temperature range of -50°C to +100°C, with higher grades offering improved thermal stability. Unlike cast PU, TPU is melt-processable and used for injection moulded seals, profiles, and custom parts. It exhibits excellent elastic recovery, low gas permeability, and good load-bearing capacity. However, TPU can degrade under long-term exposure to water, steam, or UV unless stabilised. Shore A hardness ranges from 70 to 98. TPU is used extensively in pneumatics, automotive systems, and energy sector applications. We offer injection moulded and extruded TPU sealing products across a wide range of industrial uses.
ACM is an oil-resistant elastomer used primarily in automotive and transmission applications where moderate heat and fluid resistance are required. It operates in a typical temperature range of -25°C to +150°C, with some compounds extending higher. ACM exhibits excellent resistance to hot oil, transmission fluid, and oxidation, making it ideal for engine seals and automatic gearbox components. It has good ageing stability and low compression set but limited low-temperature flexibility and poor resistance to water and steam. ACM is not compatible with brake fluids, ketones, or strong acids. It is typically used in static or mildly dynamic conditions. Shore A hardness generally falls between 50 and 80. ACM compounds can be tailored for extended life in synthetic lubricants and elevated temperatures. We supply ACM O-rings and custom moulded parts for automotive and light industrial applications requiring resistance to heat and synthetic oils.
CR, also known as Neoprene®, is a general-purpose elastomer with a balanced combination of oil, weather, and ozone resistance. It operates across a moderate temperature range of -40°C to +110°C and performs reliably in outdoor and marine environments. CR has decent resistance to aliphatic hydrocarbons, refrigerants (like ammonia and Freon), and dilute acids, making it suitable for HVAC and marine service. It is self-extinguishing and resists weathering, making it a preferred choice for sealing in exposed environments. However, CR has limited resistance to petroleum-based fuels and strong oxidising agents. It is available in a variety of hardnesses, generally 40 to 90 Shore A. While not suited to chemically aggressive environments, CR provides a well-rounded, economical sealing option. We offer Neoprene O-rings for use in electrical enclosures, HVAC systems, and legacy equipment.
FVMQ combines the low-temperature flexibility and ozone resistance of silicone with the fuel and oil resistance of fluorocarbon rubber. It operates across a wide temperature range from -60°C to +180°C, making it ideal for aerospace, automotive, and fuel system applications. FVMQ provides excellent resistance to non-polar solvents, aviation fuels, and oils, while maintaining stability under thermal cycling. It retains the flexibility of standard silicone and is often specified in systems where exposure to fuel and low temperatures coexist. FVMQ is less tear-resistant and not as durable under dynamic loading compared to FKM or HNBR. Shore A hardness typically ranges from 50 to 80. It is commonly used in aerospace fuel handling systems, vacuum equipment, and turbocharged engine components. We supply both general-purpose and aerospace-grade FVMQ compounds for specialised sealing tasks